The authors have taken the opportunity presented them by having a case of pheochromocytoma observed and diagnosed in the puerperium, of reviewing the various clinical and diagnostic features appropriate to this chromaffin tissue tumour. They also review the cardinal points in the differential diagnosis of any case of arterial hypertension discorvered in connection with pregnancy. A study of the literature shows that failure to recognise pheochromocytomata in pregnant women is accompanied by particularly hight maternal and fetal mortality. This complication of pregnancy, although rare, should be recognised by the obstetrician, who will be in a much better position early to combat and palliate the very grave threat to the mother and her baby.